This application is a 371 of PCT/JP95/01750 filed Sep. 01, 1995.
The present invention relates to a washing method and a phosphorus-free clothes detergent composition. More specifically, the present invention relates to a washing method capable of having excellent washing power with a low surfactant concentration in the washing liquid and a small dosage, and a clothes detergent composition capable of achieving given washing conditions with a small amount of dosage thereof.
Various kinds of chelating agents, ion exchange materials, alkalizers, and dispersants have been known to be used for builders to be blended in detergents. Since the phosphate-based chelating agents having tripolyphosphates as a main component thereof have good water solubility and washing power, they are preferred.
In recent years, the use of tripolyphosphates has decreased, since they can cause eutrophication in closed freshwater areas such as lakes and marshes. Instead, crystalline aluminosilicates (zeolites), typically those disclosed in Japanese Patent Laid-Open No. 50-12381, have been commonly used. In a detergent blend using the above zeolite, the standard amount of dosage for the detergent in Japan is generally about 40 g/30 L. Also, the powdery detergents available at that time had low bulk density of from 0.20 to 0.45 g/ml from the viewpoint of solubility in cold water. As a result, the standard volumetric amount of dosage was about from 90 to 200 ml/30 L, which were extremely inconvenient for handling in distribution, at stores and homes.
Therefore, an intense investigation has been made to produce compact detergents. For instance, Japanese Patent Laid-Open Nos. 62-167396, 62-167399, and 62-253699 disclose remarkable decrease in the amount of crystalline inorganic salts such as sodium sulfate used as powdery aids conventionally contained in detergents. In addition, Japanese Patent Laid-Open Nos. 61-69897, 61-69899, 61-69900, and 5-209200 disclose that by increasing the bulk density of the detergents, to thereby have a bulk density of from 0.60 to 1.00 g/ml, only a standard amount of dosage of 25 to 30 g/30 L is required, thereby making the detergents compact to have standard volumetric amount of dosage of from 25 to 50 ml/30 L.
However, in conventional detergents, a large amount of surfactants had to be blended in the detergent compositions because the mainstream idea was to make the oily components in dirt soluble by surfactants. Specifically, sebum dirt originated by human bodies, which is the most typical dirt adhered to clothes, most likely to be observed on collars and sleeves, is an example. The sebum dirt contains oily components, such as free fatty acids and glycerides, with a high content of not less than 70% (Ichiro KASHIWA et al., xe2x80x9cYukagaku,xe2x80x9d 19, 1095 (1969)). The oily components lock carbon and dirt in dust and peeled keratin, so that the resulting substance is observed as dirt. In order to wash off the sebum dirt, conventionally, detergents are designed based on a washing mechanism mainly by making these oily components soluble with micelle of surfactants, thereby detaching carbon, dirt, and keratin from clothes. This technical idea has been widely established among those of ordinary skill in the art, and even when the conventional detergents are shifted to compact detergents, substantially no changes took place in the surfactant concentration in the washing liquid. This fact is described in xe2x80x9cDictionary for Detergents and Washing,xe2x80x9d Haruhiko OKUYAMA et al., p. 428, 1990, First Edition, Asakura Publishing Company Limited, which shows that there are substantially no changes in concentrations in the washing liquid for components other than sodium sulfate.
Based on these washing principles, the surfactant concentration in the washing liquid has to be made high in order to achieve high washing power, so that a large amount of surfactants has to be blended in the detergent composition. Therefore, a drastic reduction in the standard amount of dosage of the detergents was actually difficult. In addition, the presently known production method substantially enables to increase the bulk density to a level of about at most 1.00 g/ml. Therefore, a further reduction in the standard volumetric amount was deemed to be technically extremely difficult problem.
On the other hand, crystalline silicates having particular structure disclosed in Japanese Patent Laid-Open Nos. 5-184946 and 60-74595 shows not only good ion exchange capacity and actions of alkalizers (alkaline capacity). Therefore, possibility of more compact detergents has been investigated because both of the functions of two different components, including metal ion capturing agents, such as zeolites, and alkalizers, such as sodium carbonate, can be satisfied with the above crystalline silicates alone.
For instance, Japanese Patent Laid-Open No. 6-116588 is concerned with a detergent composition containing a crystalline silicate. In Examples of this publication disclosing a more compact detergent, even in a case where the amount of the detergent composition at washing is reduced by 25%, the detergent composition has a washing power substantially the same as conventional detergent compositions. However, since the composition was formulated based on the conventional washing principle, the surfactant concentration was high, and the alkaline capacity and the ion exchange capacity were ascribed solely to the crystalline silicates contained therein. In this case, the functions of the crystalline silicates as alkalizers precede their functions as metal ion capturing agents, so that the washing power of the detergent composition was not always satisfactory. Therefore, if the amount of dosage of the detergent composition were reduced, a good washing power could not maintained.
A number of patent applications have been filed concerning the crystalline silicates disclosed in Japanese Patent Laid-Open NO. 60-74595. Japanese Patent Unexamined Publication No. 6-502199 discloses a detergent comprising a layered crystalline silicate, a zeolite, and a polycarboxylate in particular proportions, to thereby provide a detergent free from providing film layer formation on fibers and having excellent washing power and bleaching agent stability. However, under the blending conditions given in this publication, when the amount of the detergents added was reduced at washing, the alkaline capacity is not sufficient because the amount of silicate in the builder composition is small, thereby making it impossible to maintain good washing power. Also, this publication never teaches the technical idea that an excellent washing power is exhibited in a small amount of dosage of detergents.
The technical idea that an excellent washing power is exhibited in a small amount of dosage of detergents as in the present invention cannot be found for detergents containing crystalline silicates disclosed in Japanese Patent Unexamined Publication 6-500141, Japanese Patent Laid-Open Nos 2-178398 and 2-178399. Rather, in the case where the amounts of the detergent compositions shown in each of Examples are reduced, the washing power is lowered.
Further, U.S. Pat. No. 4,303,556 and EP-A-0550048 disclose detergent compositions comprising surfactants, aluminosilicates, and alkali metal silicates. However, these publications do not disclose that the detergent compositions show high washing power even when the surfactant concentration is low.
An object of the present invention is to provide a washing method with excellent washing power while having a low surfactant concentration by restudying a concept of the washing mentioned above.
Another object of the present invention is to provide a phosphorus-free clothes detergent composition suitably giving characteristic washing conditions of the above washing method, to thereby make it possible to wash clothes with the detergent composition with a considerably smaller standard amount of dosage than conventional compact laundry detergent products requiring about 25 to 30 g/ 30 liters.
In view of the above problems, the present inventors have studied the relationship between clothes washing conditions and washing power in an extremely simplified washing system. As a result, they have developed a novel detergent composition which is sufficient for use in small amounts.
Specifically, after intensely studying the influence of the pH and the water hardness of the washing liquid to washing power, the present inventors have found the following. The higher the pH is and the lower the water hardness is, the dependency of washing power on the concentration of the surfactant becomes lower. In the case of high water hardness with high pH, the washing power drastically lowers in spite of high pH. Also, in the case where a detergent containing a surfactant is used without adding an alkalizer, the detergent has a low washing power at a low water hardness, but its washing power dependency on the water hardness becomes sufficiently lower than that of detergents containing alkalizers. From the above results, the present inventors have aimed at the relationship between the washing liquid and dirt.
As explained in the prior art section, sebum stains, which are typical stains adhered to clothes, contain fatty acids and glycerides. The stains presumably are a mixture of these organic substances, carbon, and mud-dirt or keratin. When the washing liquid has a high pH, the content of the fatty acid increases due to a hydrolysis of glycerides, and the fatty acids proceed to form into salts with an alkali metal. Alkali metal salts of fatty acids are soaps by which suspension of dirt in the washing liquid is promoted. However, the reaction of the fatty acid forming a salt is a competitive reaction with calcium ions and magnesium ions in hard water. Since the alkali metal salts of fatty acids form scum with calcium ions and magnesium ions, in the case of high water hardness, the stains are solidified without being released from the interface with the cloth. For the above reasons, high pH and low water hardness of the washing liquid results in excellent washing power, and high water hardness of the washing liquid results in low washing power. In addition, in the case where an alkalizer is not included, since sebum stains are washed by the strength of the surfactant alone, dependency on the water hardness would be considerably smaller than those containing an alkalizer.
From the above phenomena, the present inventors have found one of the reasons why the detergent composition is able to achieve substantially the same level or better washing power compared with conventional detergents while having a lower surfactant concentration than the conventional ones. A soap obtained by saponifying the fatty acid in stains due to low water hardness and high pH has excellent washing power, thereby making it possible to use a phosphorus-free clothes detergent composition with a smaller standard amount of dosage than conventional detergents depending on surfactants. The present invention has been based upon these findings.
Accordingly, the gist of the present invention is as follows:
(1) A clothes washing method using a phosphorus-free clothes detergent composition comprising a surfactant, an alkali metal silicate, and a metal ion capturing agent other than the alkali metal silicate, the weight ratio of the alkali metal silicate to the metal ion capturing agent other than the alkali metal silicate being not more than 5/1, the method comprising the step of washing clothes in a washing liquid having the following washing conditions:
(1) The washing liquid having a pH of not less than 10.60;
(2) The washing liquid containing a material having an ion capturing capacity in an amount sufficient for theoretically changing a water hardness of water for washing to be not more than 0.5xc2x0 DH; and
(3) The washing liquid having a surfactant concentration of from 0.07 to 0.17 g/L;
(2) The washing method described in (1) above, wherein the concentration of the detergent composition in the washing liquid is from 0.33 to 0.67 g/L for the water for washing with 2 to 6xc2x0 DH;
(3) The washing method described in (1) above, wherein the concentration of the detergent composition in the washing liquid is from 0.50 to 1.20 g/L for the water for washing with 6 to 10xc2x0 DH;
(4) The washing method described in (1) above, wherein the concentration of the detergent composition in the washing liquid is from 0.80 to 2.50 g/L for the water for washing with 10 to 20xc2x0 DH;
(5) A phosphorus-free clothes detergent composition comprising components (a) to (c):
(a) a surfactant;
(b) an alkali metal silicate; and
(c) a metal ion capturing agent other than component (b),
wherein a total amount of (a), (b), and (c) components occupies 70 to 100% by weight of the entire composition, and wherein the weight ratio of component (b) to component (a) is b/a=9/1 to 1/2, and the weight ratio of component (b) to component (c) is b/c=5/1 to 1/15;
(6) The clothes detergent composition described in (5) above, wherein the weight ratio of component (b) to component (a) is b/a=9/1 to 9/11, and the weight ratio of component (b) to component (c) is b/c=4/1 to 1/15;
(7) The clothes detergent composition described in (5) or (6) above, wherein the surfactant contains a nonionic surfactant in an amount of 50 to 100% by weight;
(8) The clothes detergent composition described in (7), wherein the nonionic surfactant is a polyoxyethylene alkyl ether having an ethylene oxide moiety with an average molar number of from 5 to 15 and an alkyl moiety with average carbon atoms of from 10 to 18;
(9) The clothes detergent composition described in any one of (5) to (8) above, wherein the alkali metal silicate is contained as an alkalizer in an amount of 50 to 100% by weight of the entire alkalizer;
(10) The clothes detergent composition described in any one of (5) to (9) above, wherein the ratio of SiO2/M2O for the alkali metal silicate, M standing for an alkali metal, is from 0.5 to 2.6;
(11) The clothes detergent composition described in any one of (5) to (10) above, wherein the alkali metal silicate is crystalline;
(12) The clothes detergent composition described in (11) above, wherein the crystalline alkali metal silicate is represented by the following formula (I):
xM2Oxc2x7ySiO2xc2x7zMemOnxc2x7wH2O xe2x80x83xe2x80x83(I) 
wherein M stands for an element in Group Ia of the Periodic Table; Me stands for one or more elements selected from the group consisting of Group IIa, IIb, IIIa, IVa, and VIII; y/x is 0.5 to 2.6; z/x is 0.01 to 1.0; n/m is 0.5 to 2.0; and w is 0 to 20;
(13) The clothes detergent composition described in (11) above, wherein the crystalline alkali metal silicate is represented by the following formula (II):
M2Oxc2x7xxe2x80x2SiO2xc2x7yxe2x80x2H2), xe2x80x83xe2x80x83(II) 
wherein M stands for an alkali metal; xxe2x80x2 is 1.5 to 2.6; and yxe2x80x2 is 0 to 20;
(14) The clothes detergent composition described in any one of (5) to (13) above, wherein the (c) metal ion capturing agent contains a carboxylate polymer having a Ca ion capturing capacity of not less than 200 CaCO3 mg/g in an amount of not less than 10% by weight;
(15) The clothes detergent composition described in any one of (5) to (14) above, wherein the (c) metal ion capturing agent comprises:
(c-i) a carboxylate polymer having a Ca ion capturing capacity of not less than 200 CaCO3 mg/g; and
(c-ii) an aluminosilicate having an ion exchange capacity of not less than 200 CaCO3 mg/g and having the following formula (III):
xxe2x80x3(M2O)xc2x7Al2O3xc2x7yxe2x80x3(SiO2)xc2x7wxe2x80x3(H2O), xe2x80x83xe2x80x83(III)
wherein M stands for an alkali metal; xxe2x80x3, yxe2x80x3, and wxe2x80x3 each stands for a molar number of each component; xxe2x80x3 is from 0.7 to 1.5; yxe2x80x3 is from 0.8 to 6.0; and wxe2x80x3 is from 0 to 20, and wherein the weight ratio of (c-i) component to (c-ii) component is (c-i)/(c-ii)=1/20 to 4/1, and the total amount of (c-i) and (c-ii) components occupies 70 to 100% by weight based on the (c) metal ion capturing agent; and
(16) The washing method described in (1) above, wherein the clothes detergent composition described in any one of (5) to (15) above is used.